Recording systems include a heat transfer recording system. Since this system can record on plain papers and the record formed is excellent in storability, the system has been widely used for word processors, fascimiles, label printers, vending machines, etc., each using thermal head.
As a heat transfer medium which is used for the heat transfer recording system, a recording medium having formed on a base material an ink layer containing a binder mainly composed of wax or a resin compounded with a coloring agent has been widely used, but such a recording medium has the disadvantage that when images transferred onto a recording paper from the heat transfer medium are rubbed, the ink film formed on the recording paper is removed or the images are stained to reduce the image quality of the transferred images.
Accordingly, for overcoming this disadvantage, various heat transfer media having an almost colorless fusible transfer layer between the ink layer and the base material have been investigated. Using this heat transfer medium, the images transferred onto a recording paper are composed of ink film portions and colorless film portions overcoated on the ink film portions, and the occurrence of stains by rubbing, etc. can be prevented.
However, many of the ink layers of such heat transfer media are compatible with heat fusible transfer layers used as the colorless interlayers and in this case, both layers are intermixed with each other on transfer of images to reduce the distinctness of prints formed. Furthermore, a heat transfer medium of reducing the melt viscosity of the colorless interlayer for improving the peeling of the ink layer from the base material by the colorless interlayer is known. However, when the application voltage on a thermal head is changed in case of using this heat transfer medium, the transferred images wherein image portions are blurred or image portions are connected with each other to fill blank portions (corresponding to FIG. 4 (c)) are formed to give transferred images having poor image quality.